Improving diet quality is a central component in the fight against obesity. One hotly debated topic is the role of prices for healthy foods and nutritionally less desirable foods, but little data is available. Congress has asked USDA to conduct a pilot study that provides discounts on healthy foods, but this project has not started yet and will be limited to selected individuals in a single county in Massachusetts. We propose to analyze data from a much larger program that was started in 2009 by the South African health insurance company Discovery. Discovery's HealthyFood program provides rebate of up to 25% on healthy items through a nationwide supermarket chain and presently enrolls about 200,000 households. Food items eligible for a discount on the HealthyFood benefit were selected in agreement with international and US dietary guidelines and are marked on cash register receipts and on the shelves. We will consider the overall impact of the program on purchases, diets, and health outcomes, and also try to separate out the effects of the financial incentives from the educational component and environmental changes that affect the whole population. Our primary statistical approach is difference-in-difference analysis (pre/post of individuals becoming eligible for benefit with control groups), complemented with additional statistical analyses to address selection biases. Data sources include both individual health surveys, sales data from supermarkets (individual line items and linkable to individuals), and health care claims.